Hybrid hypergolic rocket propellant systems and method



United States Patent 3,287,911 HYBRID HYPERGOLIC ROCKET PROPELLANT SYSTEMS AND METHOD Alfred Klein, 1265 47th St., Brooklyn, N.Y. No Drawing. Filed Dec. 5, 1963, Ser. No. 328,197 5 Claims. (Cl. 60-220) This invention relates to a hypergolic fuel-oxidizer system, possessing superior capabilities and versatility and lending itself very advantageously to be adapted for hybrid rockets, ram rockets and turbo air rockets.

In its more particular aspect the present invention is concerned with a fuel-oxidizer system employing alkali metal carbides and acetylides, and alkali earth metal carbides as the fuel component.

In the brief history of chemical rocket development major contenders for a practical propulsion system are the liquid bi-propellant systems, the liquid mono-propellant systems and solid bi-propellant systems. The difficulty in controlling and throttling the thrust of these rocket systems are inherent in the nature of these systems. For instance, with bi-propellant liquid rockets, a precise balance of fuel and oxidizer must be maintained throughout the complete thrust range, therefore requiring a complex and expensive apparatus for controlling this balance and sensing changes in this system. Even so, there is always a danger of overconcentration of an explosive mixture of volatile fluids concentrating in the combustion chamber. The use of cryogenic fuel and oxidizers or highly corrosive fuel and oxidizers further highly complicate the practical application of this system.

In the solid propellant rocket, it is even more difficult to throttle and control the thrust of the propulsion. There is always the danger of an accidental ignition since the fuel and oxidizer are always intimately mixed, therefore, requiring exceptional care and expense in the preparation and maintenance of this system.

In liquid mono-propellant systems, although it is easy to throttle and control the thrust of propulsion, the specific impulse is about half of bi-propellant systems.

There are presently major efforts being expanded to develop suitable systems to overcome the shortcomings and deficiencies of the cited propulsion systems. This invention overcomes these disadvantages by the use of a combination of solid fuels and liquid oxidizer forming a hybrid system.

Accordingly, it is one of the principal objects of the present invention to provide a unique and simple hybrid system of propulsion in which the solid fuel is comprised of an alkali metal carbide and/or an alkali earth metal carbide and an oxidizer of hydrogen peroxide.

Hybrid systems heretofore utilizing hydrogen peroxide as an oxidizing agent must pass the hydrogen peroxide through a decomposition chamber before entering the combustion chamber. The decomposition chamber is a chamber which contains catalysts in various forms of suspension. These catalysts break down the hydrogen peroxide into water and oxygen. These exhaust products consequently ignite and burn the fuel. It is accordingly, a further object of this invention to provide a rocket propulsion system that does not require a decomposition chamber for the catalytic decomposition of the hydrogen peroxide and nevertheless, produces hypergolic combustion upon the hydrogen peroxide making direct contact with the solid fuel charge.

A still further object of the present invention is to render this fuel-oxidized system substantially instantaneously ignitable resulting from physical contact of the oxidizer with the alkali metal carbide or alkali earth metal carbide with suitable catalysts and additives being incorporated within the solid fuel charge.

A yet further object is to provide a propulsion system with the unique feature of requiring only one pumping system to control starting, throttling, stopping and restarting.

Furthermore, it is the object of the invention to provide a system whereby both the fuel and oxidizer components are easily storable, relatively non-toxic, non-corrosive, non-volatile and easy to prepare.

One of the inherent advantages of the present invention is the ability to adjust and vary the proportion of oxidizer to fuel so as the exhaust products will contain a high percentage of hydrogen and carbon monoxide which can subsequently be burned in a ram rocket.

Accordingly, it is the principal object of the present invention to provide a highly desirable fuel-oxidizer system which is readily and safely stored prior to use, hypergolic in nature and which possesses a high degree of combustion, uniformity and stability and is adaptable to a broad range of applications.

Further objects and advantages of this invention will become apparent to those skilled in the art from the following discussion and appended claims.

This invention is substantially a hybrid system in which the fuel consists of a solid mold with passageway therein to allow contact with an oxidizer. The fuel itself is a mixture of finely powdered from 30-100 microns of an alkali metal carbide or an alkali earth metal carbide such as lithium carbide or calcium carbide. This powder is molded into a solid matrix by using a suitable plastic binder. This plastic binder should sublime below 600 degrees C. As an example, methacrylate or melamine plastics may be used.

A solid chemical catalyst is added to the fuel that will decompose the hydrogen peroxide oxidant. An example is potassium cuprocyanide or any suitable catalyst that can be safely mixed and stored with the above-mentioned fuels and catalytically decompose the hydrogen peroxide.

An additive is incorporated to accelerate the rate of combustion such as an alkali metal azide.

The oxidizer is from 60100% concentration by weight hydrogen peroxide.

This hydrogen peroxide is sprayed directly into the passageways of the fuel element without any intermittent decomposition chambers.

As the hydrogen peroxide is sprayed upon the surface of the fuel element the combination of fuel, catalyst and additive react hypergolically and form oxides of carbon, alkali metals, alkali earth metals, and hydrogen, acetylene and water. Hydrogen, carbon monoxide and acetylene react with additional hydrogen peroxide or atmosphere air for more complete combustion. The heat of this combustion may reach 6000 degrees F. These hot exhaust gases can be adapted to be used for propulsion by incorporating many of the presently existing rocket nozzle systems. The oxidizer may be sprayed in by usingmany of the conventional mono-propellant peroxide pumping systems, well known in state of the art.

The fuel element is prepared in the following manner. From -80% by weight consists of the alkali metal carbide or alkali earth metal carbide or mixtures thereof, from 5-15 catalyst, from 0-15% alkali azide and from 10-30% organic binder that would sublime when heated under 600 degrees centigrade.

The fuel which is the alkali metal carbide or alkali earth metal carbide is ground in a thoroughly dry and cool atmosphere to about 30l00 microns, lubricated while grinding with a volatile non-inflammable organic liquid to minimize any possible reaction of moisture with the fuel. The fuel is filtered out and the excess organic liquid is removed by either vacuum distillation or ordinary distillation methods.

The catalyst and the alkali azide is prepared in the same manner.

The binder is dissolved in a solvent and the catalyst and alkali azide are mixed and dispersed into the dissolved binder. The powdered fuel is then introduced and blended into this liquid to form a homogeneous mass. This mass is cured by slow evaporation and is compressed with moderate heat and pressure enough to soften the plastic binder into the desired mold. It is understood this operation should take place in a dry and cool atmosphere. The amount of solvent used for the binder depends on the particular working conditions employed for blending the fuels.

As a specific example 140 grams of calcium carbide was ground in a mortar using kerosene as a volatile lubricant in a dry chamber until a very fine powder was obtained. 35 grams of powdered Plexiglas was dissolved in approximately 100 cc. of methylene chloride. 15 grams of potassium cuprocyanide was dried in an oven and ground into a fine powder and was mixed with the binder. grams of sodium azide was ground up into a fine powder while lubricated with methylene chloride to prevent accidental detonation and mixed directly into the solvent. This mixture of solvent, binder, catalyst and sodium azide was blended with the calcium carbide in a dry atmosphere. This plastic mixture was allowed to gradually evaporate while blending and mixing until it was viscous enough to be placed into a mold for curing. A simple cylindrical mold was used forming a simple cylindrical shape. When the mold was completely dry the outside surface was coated with epoxy and fiberglass to protect the outside surface from atmospheric moisture.

A hole was drilled through the center of this cylinder and this cylindrical fuel element was incorporated into a rocket system whereby a 90% hydrogen peroxide solution was sprayed into the hole of the cylindrically shaped fuel element. Without adding any form of ignition system the fuel ignited spontaneously upon contact with the hydrogen peroxide producing a very hot and powerful exhaust. The rate of combustion was easily controlled by controlling the amount of hydrogen peroxide being sprayed onto the fuel element. Furthermore by stopping the spray of hydrogen peroxide the reaction stopped and in turn was easily restarted by restarting the spray of hydrogen peroxide into the fuel element. This was done many times.

This fuel-oxidizer system lends itself to be incorporated in a ram rocket system since the proportions of oxidizer to fuel can be adjusted so as the heat of the reaction would be sufficient to sublime and volatize the binder and introduce into the rocket chamber an excess of fuel such as the carbides which would produce increased proportions of carbon monoxide, hydrogen and acetylene. This excess fuel would be burned with air in a ram rocket. The incorporation of a ram rocket in conjunction with this hybrid rocket system will highly increase its specific impulse.

The application of my alkali metal carbide and hydrogen peroxide fuel-oxidizer system to ram rockets depends upon the following reactions:

A LizCz H2O L120 2C H2 C-l-HzO H2+CO LizCz 3I'IzO Lino 3H; 2C0

z z 311202 ZLizO 400 3H2 LizCz 511 0; LizO 2602 51120 Reactions (1) to (5) are adaptable to a ram rocket system, reacting with atmospheric oxygen as in reaction (7). In order for reactions (1) to (5) to predominate so as to be adapted for ram rockets, the ratio of oxidizer to fuel is adjusted by introducing water into the hydrogen peroxide spray.

The rate of combustion is controlled by the percentage of the additive lithium azide (LiNg). An increase in the percentage by weight of lithium azide in the solid fuel matrix will cause an increase in the rate of disintegration of said solid fuel matrix, during combustion.

Lithium carbide was formed by the process of dissolving lithium metal in liquified ammonia and bubbling acetylene gas through this solution. Lithium acetylide (LiC H) which is first formed, decomposes when it is isolated. The decomposition products are a mixture of lithium carbide and lithium acetylide.

Powdered lithium carbide and lithium acetylide was blended with polymethyl methacrylate to form the solid phase of the hybrid rocket propulsion system. This carbide and acetylide with dissolved polymethyl methacrylate dissolved in methylene dichloride, a catalyst potassium cuprocyanide and an additive lithium azide were mixed togetherrand molded in a cylindrical form in a dry atmosphere. When concentrated hydrogen peroxide was sprayed onto the inner cylindrical Wall ignition took place substantially instantaneously, producing large volumes of gaseous material.

Since the molecular weight of lithium oxide is considerably less than the other alkali metal oxides and alkali earth metal oxides it is highly advantageous to incorporate lithium carbide and lithium acetylide into the solid phase of this hybrid fuel oxidizer propulsion system.

It is to be understood that although the compositions and process have been described with specific reference to particular embodiment thereof, it is not to be limited, since changes and alterations therein may be made which are within the full intended scope of this invention, and that the use of the products is not limited to any specific application.

What I claim is:

1. A method of applying thrust to a mass by a combustive reaction comprising, introducing an oxidant onto and making contact with a fuel element in a combustion chamber of a reaction motor in proportions effective to be used in air exchange propulsion systems, said oxidant comprising hydrogen peroxide, and said fuel element comprised of a mixture consisting of %85% by weight of a powdered material selected from the group consisting of alkali metal carbide, alkali earth metal carbide and mixtures thereof, 5%15% by weight of a powdered material suitable to be used as a catalyst for decomposing said oxidizer, 0%15% by weight of an additive consisting of powdered material, 10%30% by weight of a material suitable to be used as a binder, said mixture being formed into a solid matrix said oxidizer when brought into contact with said solid matrix, producing a combustive reaction and said additive causing an acceleration of said combustive reaction, wherein the said proportions of said fuel element to said oxidant is such so that the gas products resulting from said combustive reaction are in excess of 40% by molar volumes of hydrogen, carbon monoxide and acetylene.

2. A method according to claim 1 wherein the ratio of oxidizer to fuel is controlled by introducing water into the hydrogen peroxide oxidizer to produce an acetylene reaction with the carbides.

3. A method according to claim 1 wherein said oxidizer is hydrogen peroxide and said catalyst is potassium cuprocyanide.

4. A method according to claim 1 wherein said additive is alkali metal azide.

5. A method of applying thrust to a mass by a combustive reaction comprising, introducing an oxidant into and making contact with a fuel element 'in a combustion chamber of a reaction motor said oxidant comprising hydrogen peroxide and said fuel element comprised of a mixture consisting of 70%85% by weight of a powdered material selected from the group consisting of alkali metal carbide, alkali earth metal carbide and mixtures thereof, 5%15% by weight of potassium cuprocyanide, 0%l5% by weight of an alkali metal azide, 10%30% by Weight of a material suitable to be used as a binder, said mixture being formed into a solid matrix, producing a combustive reaction and said alkali metal azide causing an acceleration of said combustive reaction.

References Cited by the Examiner UNITED STATES PATENTS 2,791,883 5/1957 Moore et al 14987 X 2,984,973 5/ 1961 Stegelrnan.

3,017,748 1/ 1962 Burnside 603 5.6

3,083,527 4/1963 Fox 149-2 X 3,158,992 12/1964 Hodgson 60-35.4

FOREIGN PATENTS 1,117,015 11/1961 Germany.

OTHER REFERENCES Zaehringer: Solid Propellant Rockets, Second Stage, American Rocket Co., Box 1112, Wyandotte, Mich., 1958, pp. 229, 230.

BENJAMIN R. PADGETT, Primary Examiner.

LEON D. ROSDOL, Examiner. 

5. A METHOD OF APPLYING THRUST TO A MASS BY A COMBUSTIVE REACTION COMPRISING INTRODUCING AN OXIDANT INTO AND MAKING CONTACT WITH A FUEL ELEMENT IN A COMBUSTION CHAMBER OF A REACTION MOTOR SAID OXIDANT COMPRISING HYDROGEN PEROXIDE AND SAID FUEL ELEMENT COMPRISED OF A MIXTURE CONSISTING OF 70%-80% BY WEIGHT OF A POWDERED MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL CARBIDE, ALKALI EARTH METAL CARBIDE AND MIXTURES THEREOF, 5%-15% BY WEIGHT OF POTASSIUM CUPROCYANIDE, 0%-15% BY WEIGHT OF AN ALKALI METAL AZIDE, 10%-30% BY WEIGHT OF A MATERIAL SUITABLE TO BE USED AS A BINDER, SAID MIXTURE BEING FORMED INTO A SOLID MATRIX, PRODUCING A COMBUSTIVE REACTION AND SAID ALKALI METAL AZIDE CAUSING AN ACCELERATION OF SAID COMBUSTIVE REACTION. 